【作者】 姚文志；

【导师】 李思殿；

【作者基本信息】 山西大学 ， 无机化学， 2010， 博士

【摘要】 借助理论方法预测新颖团簇的结构和性质是计算化学的主要任务之一。理论计算在促进团簇化学自身发展的同时,也可以为实验合成新型材料提供新的探索方向。20世纪80年代,等瓣相似性(Isolobal Analogy)理论的提出极大地促进了原子簇化学的发展。论文围绕BO、BS自由基及Au原子与H原子的等瓣相似性,对新颖硼氧团簇、硼硫团簇及硼金团簇的结构和性质进行了系统探讨,研究结果对硼团簇发展具有重要意义。本论文采用密度泛函理论和波函数方法对硼氧、硼硫、硼金及铝金团簇的阴离子和中性分子的几何结构、电子结构、成键特征、热稳定性进行了理论研究,并计算了阴离子基态结构的电子剥离能,为其光电子能谱实验表征提供依据。主要研究内容及结论如下：1富硼硼氧团簇(B5O4-/0)结构和性质的理论研究用DFT-B3LYP和MP2(Full)方法对硼氧团簇B5O4-/0的几何结构和电子结构进行了系统研究。计算结果表明B5O4-阴离子的基态结构是一个完美的正四面体(B(BO)4-),每个BO自由基以端基方式与中心B原子形成σ键,其成键方式与BH4-类似,进一步证明了BO/H的等瓣相似性。而B5O4中性分子的基态结构则接近于平面构型,对称性为Cs,其中含三个端基-BO,一个-O-桥氧。当TdB5O4-失去一个电子时,其中一个BO基团在分子内部发生转移形成CsB5O4中性分子。计算表明TdB5O4-阴离子的垂直单电子剥离能很高(VDE=7.32-7.85 eV),在2000cm-1处有-B=O基团的伸缩振动特征峰。在B5O4-团簇基态结构基础上,进一步引入碱金属Li+反离子生成中性“盐”B5O4Li。计算结构参数、偶极矩值等证明B5O4-是稳定的结构单元,以“超原子”形式存在于中性盐分子中。本工作提供了以B5O4-为结构单元形成硼羰基晶体材料的可能性。2富氧硼氧团簇(B204-/0、B30440、B3O5-/0和B306-/0)结构和稳定性的理论研究在DFT-B3LYP和CCSD(T)//B3LYP水平上首次对富氧的硼氧团簇B2O4-/0、B3O4-/0、B3O5-/0、B3O6-/0的结构和稳定性进行了理论探索。研究结果表明,富氧团簇阴离子和中性分子的基态结构存在较大差别,BO3三角形结构单元、-BO端基及-O-氧桥在这些结构中共存并相互竞争。富氧微团簇倾向于形成BO3三角形平面结构单元,这一趋势与硼氧化物的最稳定块体结构-B2O3玻璃体的结构特点相一致。对富氧硼氧团簇的研究结果有待实验验证。3硼硫团簇(B4S20/-/2-和B5S40/-)结构和稳定性的理论研究采用DFT-B3LYP和CCSD(T)//B3LYP方法对B2(BS)20/-/2-和B(BS)40/-的几何结构和电子性质进行了研究。计算结果表明B2(BS)2-([S=B-B≡B-B=S]-)(D∞h,2Πu)和B2(BS)22-([S=B-B≡B-B=S]2-)(D∞h,1∑g+)的基态结构均为完美的线性结构,即以含有多重键的BB单元(B≡B或者B≡B)为中心,两端各与一个BS基团连接；而TdB(BS)4-阴离子的基态是完美的正四面体构型,四个BS自由基以端基方式与B中心形成等价的四个σ键。这些结构分别与相应的D∞h B2H2-、D∞h B2H22-及Td BH4-硼氢化物类似,表明BS/H也具有等瓣相似性。然而,B4S2和B5S4中性分子结构与其阴离子差别很大：B4S2中性分子基态结构呈平面扇形(含两个相邻的-S-桥硫)；B5S4中性分子基态结构类似于风筝(B3三角形基团连两个-BS端基和两个桥硫-S-)。另外,计算了D∞hB2(BS)2-和TdB(BS)4-的电子剥离能和对称性伸缩振动频率,为其实验表征提供依据。本文初步探讨了在实验上合成含有B≡B三重键的B2(BS)2Li2和以B-为四面体中心的B(BS)4Li两种无机盐的可能性。4硼金(B2Aun-/0(n=1,2,3,5))及铝金(Al2Aun-/0(n=1,3,5))团簇的结构及性质研究采用DFT-B3LYP、MP2和CCSD(T)方法首次预测了缺电子体系B2Aun-/0(n=1,3,5)及其混合团簇B2HmAun-(m+n=3,5)的几何和电子结构,证明桥金(Bridging Gold)存在于C2v,B2Au-(1A1)、C2B2Au3-(1A)、C2v B2Au3(2B1)、C2v,B2Au5-(1A1)和CsB2Au5(2A")体系的基态结构中,即这些体系中均含有一个B-Au-B三中心二电子键(3c-2e)。在B2HmAun-(m+n=3,5)混合团簇中,通过对异构体稳定性的比较发现B-Au-B桥键比B-H-B桥键更稳定。对B-Au-B三中心二电子键的轨道组成分析表明Au 6s轨道对Au杂化轨道的贡献为92%-96%,5d轨道的贡献为8%-4%。同时,用密度泛函方法对Al2Aun-/0(n=1,3,5)团簇做了对比研究,发现虽然铝金团簇中也能形成Al-Au-Al桥键,然而各体系的基态结构与B2Aun差别较大。在Al-Au-Al键的轨道组成中,Au的6s轨道占Au杂化轨道的98%以上,5d轨道的贡献不到2%。本文还计算了阴离子的ADE和VDE值。其次,采用类似的方法对B2Au20/-／2-在不同价态下的几何结构和电子性质进行了研究,发现这三个体系的基态结构都包含多重键的BB单元,分别以直线Au-B=B-Au和链状[Au-B=B-Au]-和[Au-B≡B-Au]2-的形式存在。更多还原

【Abstract】 One of the main tasks of computational chemistry is to predict the structures and properties of novel clusters. Computational chemistry also provides new directions for synthetical chemistry and material science. The proposal of isolobal analogy by Hoffmann in 1981 has promoted the development of cluster chemistry since then. This thesis focuses on the isolobal analogies between-BO,-BS, Au atom and H atom based on intensive theoretical investigations on the binary boron oxide, boron sulfur, and boron gold clusters which are of great significance for the development of boron clusters.A systematic density functional theory and wave function theory investigation on the geometrical structure, electronic structure, bonding character and thermodynamic stabilities of B-O, B-S, B-Au and Al-Au clusters has been performed in this thesis. The adiabatic and vertical detachment energies of the concerned anions have been calculated to facilitate their future experimental characterizations. The main contents and results are as follows:1 Theoretical Investigations on Structures and Properties of Boron-rich Boron-Oxide clusters (B5O4-/0)A density functional theory and wave function theory investigation on the geometrical and electronic structures of B5O40/- clusters has been performed. B5O4- anion proves to possess a perfect tetrahedral ground state of Td B(BO)4- (1A1) analogous to BH4- with four equivalent-BO terminals around the B center, while B5O4 neutral favors a slightly off-planed Cs B(BO)4 (2A’) which contains three-BO terminals and one-O-bridge. An intramolecular BO radical transfer occurs from Td B(BO)4 to Cs B(BO)4 when one electron is detached from the anion. The one-electron detachment energies of the B(BO)4- anion and the characteristic stretching vibrational frequencies of-B=O groups at about 2000 cm-1 have been calculated to facilitate future experimental characterization of these clusters. A neutral B(BO)4-Li+ ion-pair is formed when a countercation Li+ is incorporated. Tetrahedral B5O4- is a stable structure unit as evidence by the calculated structural parameters and dipole moment. Therefore, B5O4-, which behaves like a superatom, can be used as a building block to construct new solid state materials.2 Theoretical Investigations on Structures and Stabilities of Oxygen-rich Boron-Oxide clusters (B2O4-/0, B3O4-/0, B3O5-/0 and B3O6-/0)The structures and stabilities of the oxygen-rich B2O4-/0, B3O4-/0, B3O5-/0, and B3O6-/0 binary clusters have been investigated for the first time at both DFT-B3LYP and CCSD(T)//B3LYP levels. The ground-state structures of the anions and their neutrals appear to be much different, with the triangular BO3 unit, terminal-BO, and bridging-O-coexisting and competing with one another. The preference of BO3 planar triangles in O-rich microclusters agrees with the structural character of the glassy B2O3 which represents the most stable boron oxide in the bulk. The results obtained for O-rich boron clusters invite experimental confirmations.3 Theoretical Investigations on Structures and Stabilities of Boron-Sulfur clusters (B4S20/-/2- and B5S40/-)A density functional theory investigation on the geometrical and electronic properties of B4S20/-/2-(B2(BS)20/-/2-) and B5S40/- (B(BS)40/-) clusters has been performed in this work. Both the doublet B2(BS)2-([S=B-B(?)B-B=S]-) (D∞h,2Πu) and singlet B2(BS)22- ([S=B-B=B-B=S]2-) (S∞h,1Σg+) proved to have perfect linear ground-state structures containing a multiply bonded BB core (B(?)B or B=B) terminated with two BS groups, while Td B(BS)4- turned out to possess a perfect tetrahedral B center directly corrected to four BS groups, similar to the corresponding boron hydride molecules of D∞h B2H2-, D∞h B2H22-, and Td BH4-, respectively. B4S2 and B5S4 neutrals, however, appeared to be much different:they favor a planar fan-shaped C2v B4S2 (a di-S-bridged B4 rhombus) and a planar kite-like C2v B5S4 (a di-S-bridged B3 triangle bonded to two BS groups), respectively. One-electron detachment energies and symmetrical stretching vibrational frequencies are calculated for D∞h B2(BS)2- and Td B(BS)4- monoanions to facilitate their future characterizations. Neutral salts of B2(BS)2Li2 with a elusive B=B triple bond and B(BS)4Li containing a tetrahedral B- center are predicted possible to be targeted in future experiments.4 Theoretical Investigations on Structures and properties of Boron-Gold clusters (B2Aun-/0 (n=1,2,3,5)) and Aluminum-Gold clusters (Al2Aun-/0 (n=1,3,5))A systematic density functional theory and wave function theory investigation on the geometrical and electronic structures of the electron-deficient diboron aurides B2Aun-/0 (n=1,3,5) and their mixed analogues B2HmAun-(m+n=3,5) has been performed in this chapter. Ab initio theoretical evidences strongly suggest that bridging gold atoms exist in the ground states of C2v B2Au-(1A1), C2 B2Au3-(1A), C2v B2Au3(2B1), C2v B2Au5-(1A1), and Cs B2Au5(2A") which all prove to possess a B-Au-B three-center-two-electron (3c-2e) bond. For B2HmAun- (m+n=3,5) mixed anions, bridging B-Au-B units appear to be favored in energy over bridging B-H-B, as demonstrated by the fact that the Au-bridged C2v B2H2Au- (1A1), Cs B2HAu2- (1A’), and C, B2HAu4- (1A) lie clearly lower than their H-bridged counterparts Cs B2H2Au-(1A’), C2 B2HAu2-(1A), and C2v B2HAu4- (1A1), respectively. Orbital analyses indicate that Au 6s makes about 92-96% contribution to the Au-based orbitals in these B-Au-B 3c-2e interactions, while Au 5d contributes 8-4%. The adiabatic and vertical detachment energies of the concerned anions have been calculated to facilitate their future experimental characterizations. We have done a compare research on Al2Aun-/0 (n=1,3,5) clusters at DFT-B3LYP, finding that although there is bridging Al-Au-Al units in AlAu clusters, the ground state structures are different from B-Au systems. Au 6s makes more than 98% contribution to the Au-based hybridized orbitals, while Au 5d contributes less than 2%.The geometrical and electronic structures of B2Au20/-/2- have also been explored. Their ground states proved to cantain a multiply bonded BB core, in the forms of linear Au-B=B-Au and chained[Au-B三B-Au]- and [Au-B≡B-Au]2-.更多还原